Termination for complementary signals

ABSTRACT

Apparatuses including termination for complementary signals are described, along with methods for terminating complementary signals. One such apparatus includes a termination transistor including a first node configured to receive a first complementary signal and a second node configured to receive a second complementary signal. A regulation circuit can generate a regulated voltage to render the termination transistor conductive with a substantially constant resistance. In one such method, a first complementary signal is received at a drain of a termination transistor and a second complementary signal is received at a source of the termination transistor. Energy of the complimentary signals can be absorbed when the termination transistor is rendered conductive. Additional embodiments are also described.

BACKGROUND

Non-volatile semiconductor memories (NVSMs) are widely used in manyelectronic devices such as personal digital assistants (PDAs), laptopcomputers, mobile phones and digital cameras. A NVSM can receive datafrom a bus with a termination.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments are illustrated by way of example and not limitation inthe figures of the accompanying drawings in which:

FIG. 1 is an electrical schematic diagram of an apparatus in the form ofa termination according to various embodiments of the invention;

FIG. 2 is a timing chart of complementary signals according to variousembodiments of the invention;

FIG. 3 is an electrical schematic diagram of an apparatus in the form ofa termination and a regulation circuit according to various embodimentsof the invention;

FIG. 4 is an electrical schematic diagram of an apparatus in the form ofa termination according to various embodiments of the invention;

FIG. 5 is a cross-sectional view of an apparatus in the form of afield-effect transistor (FET) according to various embodiments of theinvention;

FIG. 6 is a block diagram of an apparatus in the form of a memory deviceaccording to various embodiments of the invention;

FIG. 7 is a flow diagram of one method according to various embodimentsof the invention; and

FIG. 8 is a block diagram of an apparatus in the form of a systemaccording to various embodiments of the invention.

DETAILED DESCRIPTION

In this description, a transistor is described as being activated orswitched on when it is rendered conductive by a control gate voltagethat is greater than its source voltage by at least its thresholdvoltage. The transistor is described as being in an inactive state orswitched off when the control gate voltage is not greater than itssource voltage by at least the threshold voltage and the transistor isrendered non-conductive.

Terminations are employed to substantially reduce signal reflection on atransmission line. Signal reflection can take place on a line if animpedance of a receiver or a driver is different from a characteristicimpedance of the line. The discontinuity in the impedance causes thereflection. A signal can reflect back and forth along the line and thereflections may need to dissipate before the signal is accepted asvalid. Signal reflection can be reduced by damping and/or dissipatingthe reflections with a termination. A termination is a dissipatingand/or damping load, typically a resistive device that has an impedancethat is substantially similar to the characteristic impedance of theline. A termination can be placed in a driver or a receiver or in both adriver and a receiver connected to the line.

Termination of two lines receiving complementary signals can beaccomplished with a pair of resistances coupled (e.g., electricallyconnected, whether directly or indirectly) to each line. The pair ofresistances is coupled in series between a supply voltage and areference voltage (e.g., ground), and the line is coupled to a locationbetween the pair of resistances. The resistances dissipate power bydrawing a substantial amount of DC current from the voltage supply thatsupplies the supply voltage. The resistances can also add a significantamount of loading capacitance to a circuit. The inventors havediscovered that the challenges noted above, as well as others, can beaddressed by a termination transistor including a first node coupled toreceive a first complementary signal and a second node coupled toreceive a second complementary signal. A “node” can include, forexample, a contact, electrical junction, electrode, interconnect, line,pad, pin, region, terminal, or combinations or any or all of the above).

FIG. 1 is an electrical schematic diagram of an apparatus in the form ofa termination 100 according to various embodiments of the invention. Atermination transistor 110 has a drain coupled to a drain node 120 toreceive a first complementary signal, and a source coupled to a sourcenode 130 to receive a second complementary signal. The first and secondcomplementary signals are substantially complementary to each other, andmay or may not be perfectly complementary to each other. The terminationtransistor 110 is an n-channel transistor according to variousembodiments of the invention.

A gate 140 of the termination transistor 110 is coupled to a regulationcircuit 150 that can generate a regulated voltage on the gate 140. Theregulated voltage can render the termination transistor 110 conductivewhile the termination 100 is to receive the first and secondcomplementary signals on the nodes 120 and 130, respectively. Thetermination transistor 110 behaves as two virtual resistors in seriesthat cross-terminate each other to provide a virtual ground in a channelof the termination transistor 110. The termination transistor 110 canabsorb energy of the first and second complementary signals while thechannel remains at the virtual ground because the transitional energiesof the complementary signals are substantially equal and opposite. Thetransitional energy of one of the complementary signals is substantiallycanceled by the transitional energy of the other complementary signal inthe channel of the termination transistor 110.

The regulated voltage can maintain a conductive state of the terminationtransistor 110 through changes in process, temperature and supplyvoltage.

FIG. 2 is a timing chart 200 of complementary signals according tovarious embodiments of the invention. A first signal 210 and a secondsignal 220 are complementary digital signals that transition between alow voltage and a high voltage. The first signal 210 is high when thesecond signal 220 is low, and the first signal 210 is low when thesecond signal 220 is high. The first signal 210 and the second signal220 can be complementary clock signals according to various embodimentsof the invention. The first signal 210 and the second signal 220 can bethe first and second complementary signals received by the drain node120 and the source node 130 in the termination 100 shown in FIG. 1. Thefirst signal 210 and the second signal 220 are perfectly complementaryif complementary edges and transitions of the first signal 210 and thesecond signal 220 occur at exactly the same time. The first signal 210and the second signal 220 are not perfectly complementary if thecomplementary edges and transitions of the first signal 210 and thesecond signal 220 do not occur at exactly the same time.

FIG. 3 is an electrical schematic diagram of an apparatus in the form ofa termination and a regulation circuit according to various embodimentsof the invention. The termination includes an n-channel terminationtransistor 304 and a regulation circuit 306. The regulation circuit 306comprises a voltage follower circuit and can generate a regulatedvoltage on a line 308 coupled to a gate of the termination transistor304. The regulated voltage can maintain a conductive state of thetermination transistor 304 such that its resistance does not changesubstantially through changes in process, temperature and an input andoutput (I/O) supply voltage (e.g., VCCQ).

The termination transistor 304 has a drain coupled to a drain node 310to receive a first complementary signal, and a source coupled to asource node 312 to receive a second complementary signal. The first andsecond complementary signals are substantially complementary to eachother, and may or may not be perfectly complementary to each other. Thefirst and second complementary signals can be the first signal 210 andthe second signal 220 shown in FIG. 2.

A high gain operational amplifier 316 in the regulation circuit 306 cangenerate the regulated voltage on the line 308. The operationalamplifier 316 is coupled to a supply voltage node to receive an I/Osupply voltage, such as VCCQ, and has a non-inverting input coupled to anode of a voltage divider to receive a portion of the supply voltage,K1*VCCQ where “*” represents multiplication. The supply voltage VCCQ isreduced by a voltage divider including two resistances 322 and 326 togenerate the portion of the supply voltage K1*VCCQ. A first end of theresistance 322 is coupled to a supply voltage (VCCQ) node. A second endof the resistance 322 is coupled to the non-inverting input of theoperational amplifier 316 and a first end of the resistance 326. Asecond end of the resistance 326 is coupled to a reference (e.g.,ground) voltage node. The resistance 322 is approximately three timesthe resistance 326 such that K1 is approximately 0.25 according tovarious embodiments of the invention.

The regulated voltage on the line 308 is coupled to a drain and a gateof a diode-connected matched transistor 340. The matched transistor 340is an n-channel transistor that is matched to the termination transistor304. The termination transistor 304 and the matched transistor 340 are“matched” in that they are, for example, transistors of the same type,have substantially the same dimensions and are fabricated atsubstantially the same time in substantially the same way. Matchedtransistors are physically close in a semiconductor and have sources anddrains oriented in the same direction. A source of the matchedtransistor 340 is coupled to a first end of a resistance 352. A secondend of the resistance 352 is coupled to a first end of a resistance 358.A second end of the resistance 358 is coupled to a reference (e.g.,ground) voltage node. An inverting input of the operational amplifier316 is coupled to receive a feedback signal from a node 362 between acurrent source 366, the second end of the resistance 352 and the firstend of the resistance 358. The resistances 352 and 358 haveapproximately the same resistance R.

The operational amplifier 316 can generate the regulated voltage on theline 308 to bring the non-inverting input and the inverting input tosubstantially the same potential (current flows from the line 308through the matched transistor 340 and the resistances 352 and 358 tothe reference (e.g., ground) voltage node). The feedback signal on theinverting input of the operational amplifier 316 is approximately equalto the regulated voltage on the line 308 less a threshold voltage of thematched transistor 340 and the voltage drop across the resistance 352.The regulated voltage on the line 308 is modified by current drawn bythe current source 366 that changes with a temperature of the regulationcircuit 306 as is described below. The current source 366 has aresistance that is larger (approximately fifteen times larger) than theresistance 358 such that it draws less current than the resistance 358without substantially affecting a ratio of the resistance 352 to theresistance 358.

The regulated voltage on the line 308 is adjusted (e.g., modulated) forchanges in the supply voltage (e.g., VCCQ), temperature of theregulation circuit 306, and process associated with the fabrication ofthe termination transistor 304 and the matched transistor 340. Theregulation circuit 306 can adjust the regulated voltage in response tochanges in the supply voltage through the portion of the supply voltageK1*VCCQ coupled to the non-inverting input of the operational amplifier316. A rise in the supply voltage results in a rise in the regulatedvoltage, and a fall in the supply voltage results in a fall in theregulated voltage.

The regulation circuit 306 can adjust the regulated voltage on the line308 in response to changes in the process associated with thefabrication of the termination transistor 304. For example, a change inthe process that results in the termination transistor 304 having arelatively higher threshold voltage V_(T) results in the regulationcircuit 306 being configured to generate relatively higher regulatedvoltage as the change in process would also result in the matchedtransistor 340 having a relatively higher threshold voltage. Similarly,a change in the process that results in the termination transistor 304having a relatively lower threshold voltage V_(T) results in theregulation circuit 306 being configured to generate a relatively lowerregulated voltage due to the change in process also resulting in thematched transistor 340 having a relatively lower threshold voltage.

The regulation circuit 306 adjusts the regulated voltage on the line 308in response to changes in temperature with the current source 366 thatdraws a current I from the node 362 between the inverting input of theoperational amplifier 316, the second end of the resistance 352, and thefirst end of the resistance 358. The current I is drawn to the reference(e.g., ground) voltage node. Changes in temperature are addressedbecause mobilities of the matched transistor 340 and the terminationtransistor 304 decrease with an increasing temperature and increase witha decreasing temperature. This technique results in a resistance acrossthe termination transistor 304 that remains substantially constant whenthe termination transistor 304 is switched on.

The current source 366 is temperature dependent such that if thetemperature of an integrated circuit including the regulation circuit306 increases the current I drawn by the current source 366 alsoincreases such that a voltage drop across the resistance 352 increases.The increased voltage drop across the resistance 352 increases theregulated voltage on the line 308. If the temperature of the integratedcircuit including the regulation circuit 306 decreases, the current Idrawn by the current source 366 also decreases such that a voltage dropacross the resistance 352 decreases. The decreased voltage drop acrossthe resistance 352 decreases the regulated voltage on the line 308.

The regulated voltage on the line 308 is approximately equal to2*K1*VCCQ+V_(T)+K2*I*R. K2 is a trim constant between 0.25 and 1.0 thatcan be changed during testing of a wafer or integrated circuit chipincluding the regulation circuit 306.

FIG. 4 is an electrical schematic diagram of an apparatus in the form ofa termination 400 according to various embodiments of the invention.Four termination transistors 402, 404, 406 and 408 are coupled inparallel between a drain node 410 and a source node 412. The terminationtransistors 402, 404, 406 and 408 each have a drain coupled to the drainnode 410 to receive a first complementary signal, and a source coupledto the source node 412 to receive a second complementary signal. Thefirst and second complementary signals are substantially complementaryto each other, and may or may not be perfectly complementary to eachother. The first and second complementary signals can be the firstsignal 210 and the second signal 220 shown in FIG. 2 according tovarious embodiments of the invention. The termination transistors 402,404, 406 and 408 can be selectively switched on or off to adjust anequivalent resistance between the drain node 410 and the source node412. The equivalent resistance is the resistance of all of thetermination transistors 402, 404, 406 and 408 coupled in parallelbetween the drain node 410 and the source node 412. The terminationtransistors 402, 404, 406 and 408 are n-channel field-effect transistorsaccording to various embodiments of the invention.

Gates of the termination transistors 402, 404, 406 and 408 are eachcoupled to a respective one of four switches 422, 424, 426 and 428 thatcan couple the gates individually to a line 434 from a regulationcircuit 438. The regulation circuit 438 can generate a regulated voltageto render one or more of the termination transistors 402, 404, 406 and408 conductive while the termination 400 is operating to receive thefirst and second complementary signals. The regulated voltage can beselectively provided to the gates of the termination transistors 402,404, 406 and 408 through the respective switches 422, 424, 426 and 428.The regulated voltage can maintain a conductive state of one or more ofthe termination transistors 402, 404, 406 and 408 through changes intemperature and a supply voltage.

The switches 422, 424, 426 and 428 may be transistors and are eachswitched on or off by a respective control signal from a control logiccircuit 450. The switch 422 can couple the gate of the terminationtransistor 402 to the regulation circuit 438 or switch the terminationtransistor 402 off. The switch 424 can couple the gate of thetermination transistor 404 to the regulation circuit 438 or switch thetermination transistor 404 off. The switch 426 can couple the gate ofthe termination transistor 406 to the regulation circuit 438 or switchthe termination transistor 406 off. Finally, the switch 428 can couplethe gate of the termination transistor 408 to the regulation circuit 438or switch the termination transistor 408 off. The switches 422, 424, 426and 428 thereby control which of the termination transistors 402, 404,406 and 408 are rendered conductive to adjust the equivalent resistancebetween the drain node 410 and the source node 412. This techniqueresults in the equivalent resistance across the parallel arrangement ofthe termination transistors 402, 404, 406 and 408 remainingsubstantially constant when the termination 400 is operating.

Each of the switches 422, 424, 426 and 428 may be a transmission gateaccording to various embodiments of the invention. Each transmissiongate includes an n-channel transistor and a p-channel transistor withdrains connected together and sources connected together. Gates of then-channel transistor and the p-channel transistor can be driven bycomplementary signals.

FIG. 5 is a cross-sectional view of an apparatus in the form of afield-effect transistor (FET) 500 according to various embodiments ofthe invention. The FET 500 may be a termination transistor such as thetermination transistors 110, 304, 402, 404, 406 and 408 shown in FIGS.1, 3 and 4. The FET 500 is an n-channel FET. An N+ type source diffusionregion 514 and an N+ type drain diffusion region 516 are formed in a P−type semiconductor material, such as silicon substrate 520. Apolysilicon gate 522 is formed over a gate dielectric 524 which isformed over the silicon substrate 520 and between the source diffusionregion 514 and the drain diffusion region 516. The gate dielectric 524may comprise, for example, silicon dioxide (SiO₍₂₎), oxynitride ornitrided oxide, according to various embodiments of the invention. Atrench 528 in the silicon substrate 520 surrounds an active area of theFET 500. The source diffusion region 514 and the drain diffusion region516 are formed in the silicon substrate 520 inside the trench 528.

A gate electrode 540 can be connected to the gate 522. A sourceelectrode 550 can be connected to a contact diffusion region 554 insidethe source diffusion region 514. A drain electrode 560 can be connectedto a contact diffusion region 564 inside the drain diffusion region 516.The FET 500 is covered by a dielectric 580 that extends into the trench528 and surrounds the electrodes 540, 550 and 560. The dielectric 580may comprise, for example, silicon dioxide, silicon oxide, silica orBorophosphosilicate glass (BPSG) according to various embodiments of theinvention. The electrodes 540, 550 and 560, may comprise metal such as,for example, aluminum, copper, tungsten or polysilicon according tovarious embodiments of the invention.

During operation of the FET 500 a regulated voltage is coupled to thegate electrode 540 to induce a conductive channel 590 in the siliconsubstrate 520 between the source diffusion region 514 and the draindiffusion region 516. The silicon substrate 520 is coupled to areference voltage (e.g., ground). First and second complementary signalsare coupled to the source electrode 550 and the drain electrode 560,respectively. The first and second complementary signals aresubstantially complementary to each other, and may or may not beperfectly complementary to each other. The first and secondcomplementary signals can be the first signal 210 and the second signal220 shown in FIG. 2. The FET 500 can absorb energy of the first andsecond complementary signals while the conductive channel 590 remains ata virtual ground because the transitional energies of the complementarysignals are substantially equal and opposite. The transitional energy ofone of the complementary signals is substantially canceled by thetransitional energy of the other complementary signal in the conductivechannel 590.

The termination transistors 110, 304, 402, 404, 406 and 408 shown inFIGS. 1, 3 and 4 may be p-channel FETs according to various embodimentsof the invention. Appropriate control circuit and a regulation circuitcan be coupled to control the p-channel FETs.

FIG. 6 is a block diagram of an apparatus in the form of a memory device600 according to various embodiments of the invention. The memory device600 is coupled to a control bus 604 to receive a number of controlsignals on control signal lines 605, an address bus 606 and a data bus608 which all can be coupled to a controller (not shown). Althoughdepicted as being received on separate busses 604, 606 and 608, thecontrol signals, address signals and/or data signals can be multiplexedtogether and received on a single bus. The memory device 600 is formedin a single integrated circuit.

The memory device 600 includes one or more arrays 610 of memory cellsthat can be logically arranged in rows and in columns. The memory cellsof the array 610 can be non-volatile memory cells (e.g., flash memorycells) according to various embodiments of the invention. The memorydevice 600 can be a NOT AND (NAND) memory device. An address circuit 612can latch address signals received on address signal lines A0-Ax 614.The address signals received on the address signal lines 614 can bedecoded by a row decoder 616 and a column decoder 618 to access thearray 610 of memory cells.

Data can be read from the array 610 by sensing voltage or currentchanges in the memory cells in sense devices in a sense/cache circuit622. The sense/cache circuit 622 is coupled to read and latch a row ofdata from the array 610.

An I/O circuit 626 facilitates bi-directional data communication througha number of I/O nodes 630, 632 and 634 coupled to the data bus 608. TheI/O circuit 626 includes a number of driver and receiver circuits 640,642 and 644 to drive data on to the I/O nodes 630, 632 and 634,respectively and to receive data from the data bus 608 through the I/Onodes 630, 632 and 634. Each driver and receiver circuit 640, 642 and644 includes a respective termination 650, 652 and 654 to dissipateand/or dampen signal reflections in the I/O nodes 630, 632 and 634. Eachtermination 650, 652 and 654 may comprise the termination transistor 110shown in FIG. 1 or the termination transistor 304 shown in FIG. 3 or theswitches 422, 424, 426 and 428 and the termination transistors 402, 404,406 and 408 shown in FIG. 4.

A control circuit 658 is configured to facilitate operations of thememory device 600, such as writing data to and/or erasing data from thememory cells of the array 610. Data can be transferred between thesense/cache circuit 622 and the I/O circuit 626 over N signal lines 664.A regulation circuit 667 is configured to generate a regulated voltagethat can render termination transistors in the terminations 650, 652 and654 conductive with a substantially constant resistance. A resistance issubstantially constant if it is within plus or minus ten percent (10%)of a target resistance. The regulation circuit 667 may comprise theregulation circuit 150 shown in FIG. 1 or the regulation circuit 306shown in FIG. 3 or the regulation circuit 438 shown in FIG. 4. Theregulated voltage can be provided from the regulation circuit 667 to theterminations 650, 652 and 654 through a control logic circuit 668. Thecontrol logic circuit 668 can provide control signals over lines 670 and672 to the terminations 650, 652 and 654 to control switches for thetermination transistors such as the switches 422, 424, 426 and 428 shownin FIG. 4.

FIG. 7 is a flow diagram of one method 700 according to variousembodiments of the invention. In block 710, the method 700 begins. Inblock 720, a first complementary signal is received at a drain of atermination transistor. In block 730, a second complementary signal isreceived at a source of the termination transistor. Energy of the firstcomplementary signal and the second complementary signal can be absorbedin the termination transistor when the termination transistor isrendered conductive. In block 740, the method 700 ends. Variousembodiments may have more or fewer activities than those shown in FIG.7. The activities shown may be accomplished in the illustrated order, orin another order. Some activities may be substituted for others.

FIG. 8 is a block diagram of an apparatus in the form of a system 800according to various embodiments of the invention. The system 800 mayinclude a processor 810, a memory device 820, a memory controller 830, agraphic controller 840, an I/O controller 850, a display 852, a keyboard854, a pointing device 856, and a peripheral device 858. A bus 860couples all of these devices together.

A clock generator 870 can be coupled to the bus 860 to provide a clocksignal to at least one of the devices of the system 800 through the bus860. The clock generator 870 may include an oscillator in a circuitboard such as a motherboard. Two or more devices shown in system 800 maybe formed in a single integrated circuit chip. The bus 860 may be usedto interconnect traces on a circuit board and may comprise one or morecables. The bus 860 may couple the devices of the system 800 by wirelessmechanisms, such as by electromagnetic radiation, for example, radiowaves. The peripheral device 858 coupled to the I/O controller 850 maybe a printer, an optical device such as a CD-ROM and a DVD reader andwriter, a magnetic device reader and writer such as a floppy diskdriver, or an audio device such as a microphone.

The processor 810 includes a termination 882 to dampen and/or dissipatesignal reflections inside the processor 810 or on the bus 860. Thememory device 820 includes a termination 886 to dampen and/or dissipatesignal reflections inside the memory device 820 or on the bus 860. Eachtermination 882 and 886 may comprise the termination transistor 110 andthe regulation circuit 150 shown in FIG. 1 or the termination transistor304 and the regulation circuit 306 shown in FIG. 3 or the switches 422,424, 426 and 428, the termination transistors 402, 404, 406 and 408, theregulation circuit 438 and the control logic circuit 450 shown in FIG.4.

The system 800 represented by FIG. 8 may include computers (e.g.,desktops, laptops, hand-helds, servers, network appliances, routers,etc.), wireless communication devices (e.g., cellular phones, cordlessphones, pagers, personal digital assistants, etc.), computer-relatedperipherals (e.g., printers, scanners, monitors, etc.), entertainmentdevices (e.g., televisions, radios, stereos, tape and compact discplayers, video cassette recorders, camcorders, digital cameras, MP3(Motion Picture Experts Group, Audio 3) players, video games, watches,etc.), and the like.

The inventors believe that one or more of the various embodiments of theinvention shown and described herein can be used to, for example,terminate lines carrying complementary signals with substantiallyreduced loading capacitance and/or power dissipation.

Although specific embodiments have been described, it will be evidentthat various modifications and changes may be made to these embodiments.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b), requiring an abstract that allows the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit theclaims. In addition, in the foregoing Detailed Description, it may beseen that various features can be grouped together in a singleembodiment for the purpose of streamlining the disclosure. This methodof disclosure is not to be interpreted as limiting the claims. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separate embodiment.

What is claimed is:
 1. An apparatus comprising: a plurality oftermination transistors coupled in parallel including a first nodeconfigured to receive a first complementary signal and a second nodeconfigured to receive a second complementary signal wherein the firstcomplementary signal and the second complementary signal aresubstantially complementary to each other; a voltage follower circuit togenerate a regulated voltage; and a plurality of switches, each of theplurality of switches coupled between the voltage follower circuit and agate of a respective one of the termination transistors to selectivelyprovide the regulated voltage to the gate of the respective terminationtransistor to render the respective termination transistor conductivewith a substantially constant resistance.
 2. The apparatus of claim 1,wherein the voltage follower circuit further comprises an operationalamplifier having a non-inverting input coupled to a node of a voltagedivider, an inverting input coupled to receive a feedback signal and anoutput, the operational amplifier to generate the regulated voltage onthe output.
 3. The apparatus of claim 1, wherein each of the terminationtransistors comprises an n-channel field-effect transistor.
 4. Theapparatus of claim 1, wherein each of the termination transistorscomprises a p-channel field-effect transistor.
 5. An apparatuscomprising: a termination transistor including a first node configuredto receive a first complementary signal and a second node configured toreceive a second complementary signal wherein the first complementarysignal and the second complementary signal are substantiallycomplementary to each other; and a voltage follower circuit coupled to agate of the termination transistor to maintain the terminationtransistor conductive with a substantially constant resistance duringchanges in a temperature of an integrated circuit including the voltagefollower circuit and/or a supply voltage received by the voltagefollower circuit, wherein the voltage follower circuit further comprisesan operational amplifier having a non-inverting input coupled to a nodeof a voltage divider, an inverting input coupled to receive a feedbacksignal and an output, the operational amplifier arranged to generate aregulated voltage on the output to render the termination transistorconductive with a substantially constant resistance; and a currentsource arranged to draw a current from the output of the operationalamplifier that changes with a temperature of the integrated circuitincluding the voltage follower circuit.
 6. The apparatus of claim 5,wherein the voltage follower circuit comprises a matched transistorcoupled between the output and the inverting input of the operationalamplifier to generate the feedback signal, the matched transistor beingmatched to the termination transistor.
 7. An apparatus comprising: atermination transistor including a first node configured to receive afirst complementary signal and a second node configured to receive asecond complementary signal wherein the first complementary signal andthe second complementary signal are substantially complementary to eachother; and a voltage follower circuit coupled to a gate of thetermination transistor to maintain the termination transistor conductivewith a substantially constant resistance during changes in a temperatureof an integrated circuit including the voltage follower circuit and/or asupply voltage received by the voltage follower circuit, wherein thevoltage follower circuit further comprises an operational amplifierhaving a non-inverting input coupled to a node of a voltage divider, aninverting input coupled to receive a feedback signal and an output, theoperational amplifier to generate a regulated voltage on the output torender the termination transistor conductive with a substantiallyconstant resistance; a first resistance coupled between the matchedtransistor and the inverting input of the operational amplifier togenerate the feedback signal; and a second resistance coupled betweenthe inverting input of the operational amplifier and a reference voltagenode.
 8. A method comprising: generating a regulated voltage on a gateof a termination transistor in an integrated circuit to render thetermination transistor conductive with a substantially constantresistance; adjusting the regulated voltage in response to a change in atemperature of the integrated circuit and/or a change in a supplyvoltage received by the integrated circuit; receiving a firstcomplementary signal at a drain of the termination transistor and asecond complementary signal at a source of the termination transistor,wherein the termination transistor absorbs energy of the firstcomplementary signal and the second complementary signal, the firstcomplementary signal being substantially complementary to the secondcomplementary signal; and wherein generating the regulated voltagefurther comprises generating the feedback signal through a matchedtransistor coupled between the output and the inverting input of theoperational amplifier, the matched transistor being matched to thetermination transistor.
 9. The method of claim 8, wherein generating theregulated voltage further comprises generating the regulated voltage onan output of an operational amplifier, the operational amplifier havinga non-inverting input coupled to a node of a voltage divider and aninverting input coupled to receive a feedback signal.
 10. The method ofclaim 8, wherein generating the feedback signal further comprisesgenerating the feedback signal through a resistance coupled between thematched transistor and the inverting input of the operational amplifier.11. The method of claim 10, wherein generating the regulated voltagefurther comprises drawing a current from the output of the operationalamplifier through a current source, the current changing with atemperature of the integrated circuit.
 12. An apparatus comprising: aplurality of termination transistors coupled in parallel between a firstnode configured to receive a first complementary signal and a secondnode configured to receive a second complementary signal wherein thefirst complementary signal and the second complementary signal aresubstantially complementary to each other; a regulation circuit togenerate a regulated voltage; and a plurality of switches, each of theplurality of switches being coupled between the regulation circuit and agate of a respective one of the termination transistors to selectivelyprovide the regulated voltage to the gate of the respective terminationtransistor to render the respective termination transistor conductivewith a substantially constant resistance.
 13. The apparatus of claim 12,further comprising a control logic circuit to switch each switch on oroff.
 14. The apparatus of claim 12, wherein each switch comprises atransistor.
 15. The apparatus of claim 12, wherein each switch comprisesa transmission gate.
 16. The apparatus of claim 12, wherein eachtermination transistor comprises: a source and a drain formed in asemiconductor material, the semiconductor material being coupled to areference voltage node; and a gate formed over a gate dielectric, thegate dielectric being formed over the semiconductor material between thesource and the drain.